Relationship Between Torque Teno Sus Virus Type 2 Infection And Porcine Postweaning Multisystemic Wasting Syndrome

Postweaning multisystemic wasting syndrome (PMWS) is a multi-factorial disease caused by porcine circovirus type 2 (PCV2), and Torque teno sus virus type 2 (TTSuV2) is a potential collaborative pathogen. In this study, the load of TTSuV2 and PCV2 in sera of PMWS-suffered pigs and sub-clinical PCV2-infected pigs were determined by fluorescent quantitative (FQ-) PCR method, the difference between them was compared, and the correlation of TTSuV2 infection and PMWS occurrence was analyzed.The primers specific to TTSuV2 in the original method was adjusted, then, the original plasmid was used as templates to detect the SYBR Green I real-time PCR amplification of TTSuV2 DNA. The amplification efficiency of the new TTSuV2 SYBR Green I FQ-PCR was 99.3%. The coefficient of determination for the new standard curve was 0.998. The new assay had an accurate detectable limit of 50 copies/μL of nucleotide acid template. The melting curve, specificity and reproducibility of the new method were all very similar to the original method. However, the amplification curve was obviously improved, the accurate detectable sensitivity was increased at least 10 times and the clinical detection data was more accurate and reliable in the new assay. These data indicated that a new SYBR Green I FQ-PCR assay for quantitative detection of TTSuV2 with higher sensitivity was developed.The sera of 35 PMWS-suspected pigs and 35 healthy pigs from several pig farms was collected, the detection results by PCR assay showed that the sera of 24 PRRS-suffered pigs and 27 healthy pigs were positive PCV2. The load of PCV2 and TTSuV2 in the sera of the PCV2-positive pigs was determined with the generated SYBR Green I FQ-PCR assay of PCV2 and TTSuV2, respectively. The results showed that the load of PCV2 in the PMWS-suffered pigs sera were very significantly (P<0.01) more than the sub-clinical PCV2-infected pigs, and the load of TTSuV2 in PMWS-suffered pigs sera were significantly (P<0.05) more than the sub-clinical PCV2-infected pigs. Moreover, there was a significant correlation (P<0.05) between the load of TTSuV2 and PCV2 in PCV2-positive pigs sera, indicating a correlation between the TTSuV1 infection and the occurrence of PMWS.Taken together, a SYBR Green I FQ-PCR assay for quantitative detection of TTSuV2 was optimized, and there was correlation between the TTSuV2 infection and the occurrence of PMWS clinically.